OCULAR SPACE EXPLORATION IN THE DARK AND ITS RELATION TO SUBJECTIVE AND OBJECTIVE BODY ORIENTATION IN NEGLECT PATIENTS WITH PARIETAL LESIONS

Eye movements of neglect patients with right parietal lesions were rec orded during ocular searching for a (non-existent) target in complete darkness. With respect to the objective orientation of the sagittal mi dplane, ocular exploration was biased toward the ipsilesional side. Ho wever, in relation to the patients' subjective localization of the sag ittal midplane in space, exploratory eye movements were symmetrically distributed to the subjective ''left'' and ''right'' as observed in no n-brain-damaged controls. The present results further support the hypo thesis that the essential aspect leading to spatial neglect is a distu rbance of those cortical structures that are crucial for computing ego centric, body-centred coordinates that allow use to determine our body position in space and that are necessary for visuomotor coordination and exploration of space. In neglect patients the central coordinate t ransformation seems to work with a systematic error resulting in a dev iation of the spatial reference frame to the ipsilesional side. Conseq uences of this deviation are a displacement of subjective localization of body orientation and-to the same degree-of the spatial area in whi ch motor behavior (here exploratory eye movements) is executed.